1. Field of the Invention
The present invention relates to a mold oscillating apparatus for oscillating a mold forming a continuous casting assembly.
2. Description of the Related Art
Currently, in the continuous casting assembly, there is a known technique of using a mold oscillating apparatus for generating relative motion between a mold inner wall and a slab by oscillating a mold. By the relative motion, inflow of flux between the mold inner wall and the slab is facilitated and thereby adhesion of the slab to the mold inner wall is prevented.
For example, U.S. Pat. No. 4,678,022 discloses a mold oscillating apparatus for fixedly mounting and interconnecting a mold table in which a mold is installed and a moving bearing housing to each other by a connecting beam.
In the mold oscillating apparatus, the moving bearing housing fitted onto both end parts of a drive shaft through a bearing and moved by eccentric rotation of the drive shaft is rotatably provided, and a connecting beam is provided between the moving bearing housings arranged in the both ends of the drive shafts. One end of a lower end part of the connecting beam is fixedly mounted to one of the moving bearing housings, while the other end of the lower end part of the connecting beam is fixedly mounted to the other moving bearing housing. Meanwhile, one end to the other end of an upper end part thereof is abutted and fixedly mounted to a lower surface of the mold table.
In the mold oscillating apparatus, a tie rod for regulating lateral displacement of the mold table is arranged. Thereby, the moving bearing housing performs rotation motion by the eccentric rotation of the drive shaft, while the lateral displacement as a component of the motion transmitted from the moving bearing housing to the mold table is prevented by the tie rod, and the mold table is oscillated only in the up and down direction. The lateral displacement as a component of the motion is absorbed by deflection of the connecting beam.
However, in the connecting beam according to the above mold oscillating apparatus, although the both ends of the lower end part are supported by the moving bearing housing, a space between the moving bearing housings is not supported and held up in the air. Therefore, flexural deformation of the connecting beam due to the motion of the moving bearing housing is limited to interconnecting portions of the moving bearing housing on the both sides and the vicinity thereof. In other words, the entire connecting beam is not uniformly flexed, and an amount of the flexural deformation of the connecting beam is decreased as departing from both ends of the connecting beam (interconnecting points with the moving bearing housings). Particularly, in a large sized mold supporting apparatus, the connecting beam is also long and large. Therefore, it can be thought that a central part of such a connecting beam is not at all flexed.
As mentioned above, when “local deformation (deflection)” is only generated in the both end parts of the connecting beam, “torsional” deformation is generated between the both end parts and the central part of the connecting beam. The “local deformation (deflection)” generates the “torsion” in the connecting beam, and thereby a stress due to the “torsional deformation” is added to the connecting beam. Since the connecting beam receives a cyclic stress due to oscillation of the mold, there is a fear that even a relatively small stress generated causes crack and finally leads to breakage.
In order to avoid such a situation, it can be thought that the connecting beam is exchanged before leading to the breakage. However, since the connecting beam itself is a large sized part, the exchange is extremely uneconomical and an exchange work is not easy.
In recent years, in order to reduce an oscillation mark of the slab so as to improve quality of a surface of the slab, there is sometimes a case where a mold oscillating apparatus with high cycle of approximately 7 Hz is adapted. In such an operating method, since the number of cyclic deformation to the connecting beam in drive time of a mold drive apparatus is further increased, the life of the connecting beam before leading to the breakage is further shortened.